Patent GB-276062-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/58
Filed: 1926-05-17
Abstract: 276,062. Standard Telephones & Cables, Ltd., (Bryant, G. H.). May 17, 1926. Automatic and semi-automatic exchange systems.-In a district-office system in which local calls are set up by an operator at the main exchange over a trunk which is then released, the subscribers are connected to opposite ends of a link circuit individual to the trunk. Two arrangements aro described in detail, one for 10 subscribers with a single trunk in which the connections to the link circuit are made by means of relays, and the other for 30 subscribers with two trunks employing connectors of the type described in Specification 197,797. The latter arrangement may be extended to deal with 60 subscribers by duplicating the switches. The district-office battery is charged from the main exchange over the trunk or trunks when they are not in use. A faulty line is automatically disabled, and an operator upon making connection to such a line receives a busy signal after ringing. First arrangement, Fig. 4. Outgoing, call. When the calling subscriber removes his receiver, line relay LR energizes and connects up cut-off relay COR, extending the loop to relay PR, which energizes, locks relay COR and disconnects the exchange battery from the trunk b wire, thereby releasing relay LRE at the manual exchange to light the calling lamp CL. The operator plugs into the trunk, and sleeve relay COR1 energizes relays SYR, XR1 over the a wire, and the latter effects the operation of relays DR, DR1, OBR, IR. The operator completes the call in the usual manner. When the calling subscriber hangs up, relay PR relapses and introduces relay XR2 into the circuit over the a wire, thereby releasing relay SYR to give a clearing signal. Relay XR2 energizes and holds relay DR, which in turn holds relay COR. When the operator releases the trunk, these relays fall back. If the trunk is in use when a subscriber calls, relay PR having previously removed a short-circuit from busy relay JBR, this relay energizes in series with cut-off relay COR and connects up buzzer relay BBR, which transmits a busy tone through transformer OTB. If the trunk is seized on account of a fault on a subscriber's line, the operator releases the trunk on receiving no reply. Relay DR on falling back removes a short-circuit from relay LDR, which energizes in series with relay COR and connects itself to the line loop, and remains locked as long as the fault persists. Incoming call. When the operator plugs into the trunk, relay XR2 energizes over the a wire, and connects up relay DR, which disconnects the exchange battery from the b wire and substitutes impulse relay IR, connects up relay DR1 and advances the sequence switch to position 1¢ by means of magnet SSM and relay BR. The operator now dials over the b wire, and impulses are repeated by relay IR to magnet SM. At the end of the train, sluggish series relay AR falls back and moves the sequence switch to position 2. Relay ZR energizes over wiper a in series with cut-off relay COR of the selected line, and the latter locks and short circuits relay ZR, which relapses and drives the sequence switch to position 2¢. The operator rings the wanted subscriber over the b wire, and upon reply, relay VR energizes over the loop and advances the sequence switch to the talking pasition 3. Relay PR now energizes over the loop, cutting out relay XR2 and thereby operating relay SYR. When the called subscriber hangs up, the release of relays PR, SYR gives a clearing signal, and ali the apparatus is restored when the operator clears. If the wanted line is engaged, relay ZR is short-circuited over contacts of relays COR, DR. Buzzer relay BBR therefore operates and sends busy tone over the trunk. If the wanted line is disabled, that is, if relay LDR is operated, after cut-off relay COR energizes and the sequence switch moves to position 2¢, the b wire is connected through to relay NUR, which energizes as a result of ringing and locks in series with buzzer relay BBR to give a busy tone. Local call. The calling line is connected to the operator's position as in the case of an outgoing call. The operator dials a prefatory digit in order to advance the sequence switch to position 1¢ through relay AR, and then the wanted number, which operates magnet SM. The sequence switch moves to position 2 at the end of the train, and relay ZR energizes in series with relay AFR (relay OBR being operated), which connects up relay LCR1 of the calling line. This relay extends the calling line to the calling side of the link circuit LCL, and locks in parallel with relay COR and in series with relav LBR, which is inoperative. Relay AFR is held over the calling loop. Relay COR of the called line now energizes over wiper a, connecting the called line to the trunk and short-circuiting relay ZR to advance the sequence switch to position 2¢, in which ringing takes place. Relay VR energizes on reply, and connects up relay LCR1, LCR2 of the called line over wipers b, c to extend the called line to the called side of the link LCL, and these relays lock under the control of relay AFR. Relay LBR now receives sufficient current to operate and mark the link engaged. The sequence switch moves to the talking position 3¢, and the link is connected to the trunk at cams G, H for observation. The operator removes her plug, and the apparatus associated with the trunk is restored. Release is dependent on relay AFR, which is controlled by the calling party. If the link LCL is in use, relay LBR is operated, and in position 2, relay ZR energizes, locks and connects up buzzer relay BBR, which sends busy tone over the trunk. A similar action takes place if the wanted line is busy. Tapping and releasing a local connection. After finding that the link LCL is in use, the operator may dial three digits to advance the sequence switch to position 3¢ to connect the link to the trunk over cams G, H. On dialling a further digit, relay LRR energizes, locks and disconnects relay LBR, thus breaking down the connection. Second arrangement, Figs. 5, 6. (only one trunk BJN and the associated apparatus are shown). Outgoing call.' Line relay LR energizes starting relay CR, which connects up magnet SM1 of the line finder JF1. When the calling line is reached relay TR1 energizes in series with cut-off relay COR, and removes a short-circuit from relay SR, which energizes in series with magnet SM1 and locks in series with relav SR1 connecting the calling line to the trunk BJN. The latter relay disconnects the exchange battery from the b wire of the trunk, thereby giving a calling signal at the manual exchange. Relay PR energizes over the calling loop. The operator completes the connection in substantially the same manner as in the arrangement of Fig. 4. Relay RCR is energized to place release under the operator's control. Trunk busy relay JBR is normally short-circuited at back contacts of relay DR, so that it energizes if a subscriber calls when both the trunks are in use, and connects up buzzer relay BBR to give a busy tone. The case of a trunk being seized by a faulty line is dealt with as in Fig. 4, relay LDR becoming operated. Incoming call. Plugging into the trunk BJN causes relays XR2, DR to energize, and the latter advances the sequence switch SSM1 to position 2, and connects up relay FSR, which disconnects the exchange battery from the b wire and substitutes impulse relay IR1. Dialled impulses are repeated to move the trunk connector JC into engagement with the wanted line as in Specification 197,797. If the wanted line is not busy, the sequence switch passes to position 12 in which relay RR energizes and connects the b wire of the line to the b wire of the trunk, and the operator rings. Relay JR energizes on the reply of the called party, and drives the sequence switch into the talking position 13. Relay PR energizes over the calling loop, and serves to give a clearing signal when the called party hangs up. If the wanted line is engaged, the sequence switch stops in position 10 due to test relay VR being held over the operative test wiper in series with relay OR, which then causes buzzer relav BBR to send a busy tone over the trunk. If the wanted line is disabled, the b wire is connected by relay LDR through relay NUR, which causes a busy tone to be sent when ringing occurs. Local call. The calling line is connected to the operator's position as in the case of an outgoing call. The operator dials the prefatory digit 1, which causes impulse relay IR2 to fall back momentarily and energize switching relay LSR, which locks in parallel with relay SR, connects the calling line to the link circuit LCL and advances the sequence switch SSM2 to position 2. Relay QR energizes over the calling loop. Impulses are now repeated by relay IR2 to bring the local connector LC into engagement with the wanted line, and the talking connection is completed in position 13 if it is idle, or busy tone is sent over the trunk if it is engaged. The operator removes her plug, releasing relays XR1, IR2, DR, and relays ZSR, ZSR1 energize in parallel and lock in series with relay LSR, shortcircuiting relay SR, which disconnects the trunk from the connection and releases relays SRI, PR. When the calling party hangs up, relay QR falls back, short-circuits relay TR1 and disconnects relay COR of the called line. Relay TR1 shortcircuits switching relay LSR, which disconnects relays ZSR, ZSR1 and relay COR of the calling line. If the trunk BJN is in use when release occurs, relay DR is energized and prevents the restoration of the sequence switch SSM2 and local connector LC until the trunk is released. If the link LCL is in use, when the prefatory digit is sent, since relay ZSR1 is operated, busy relay LBR energizes instead of switching relay LSR, and busy tone is sent over the trunk. Outgoing call when the link LCL is in use. Relay LSR is energized, so that starting relay CR connects up magnet SM2 of the finder JF2. Relay TR2 connects up